i've got some questions about the story *SPOILERS*

When Marty and Doc return to 1986 to find the "Citizen Brown timeline" and Doc disappears, shouldn't the time machine disappear as well? Since the original Doc that Marty knows ceases to exist, (the Doc that created the time machine) then the time machine should cease to exist as well... right? Because Citizen Brown is the only existing Doc, and he never build the time machine. One possible solution is that the time ripple effect doesn't reach the time machine yet. But then why did it reach Doc so fast? I'm guessing that people are affected by the ripple effect much quicker. But then, in Episode 5, Hill Valley changes almost instantly while in the 2nd movie, Hill Valley changes very slowly when Marty and Doc go back to 1985 from 2015. So the speed of the time ripple effect seems to be pretty inconsistent. Or is there some sort of set of rules?

And if the time machine would cease to exist, then shouldn't all consequences of time travel meddling cease to exist as well? I would imagine that in that instant, Marty would wake up in his room that night he went to see Doc at the Twin Pines Mall and would have no memory of the events of the films or the game. It's reminiscent of a Justice League episode when they break Chronos' belt and then they revert back to the beginning of the episode before any of the time travelling took place.

One other question: what has the Doc that appears in Episode 5 experienced? I mean, that Doc is like a completely different Doc that we know from the films and from the first episodes. Let's track his life:

Emmet continues his life, pursuing his science career. He invents the time machine and the events of the film trilogy all happen. I wasn't sure if that's true at first, but it must be since Doc is married to Clara. But because of Marty's interference with his younger self, he's closer to his father and therefore he stays in Hill Valley and earns the key to the city and doesn't go around time as often as he did as the previous version of Doc. He reads Marty's note, realizing that Michael Corleone (or whoever you named Marty as in 1931) was Marty and also (I'm guessing) realizes he shouldn't go to 1931 in August (or whenever episode 1 and 2 were) because he might get arrested. But he does go in October by instructions of the note. Is this correct?

Sorry if any of this has been mentioned already, i haven't found anything on it in these forums.

Well...
I suppose Doc disappears before the Time machine because Doc directly changed and affected the whole of hill valley so in order for time to change at all he must disappear whilst it doesn't matter if the time machine has disappeared yet or not as Time travelers I think are not affected by time travel as they keep their memory so the machine has to remain as it is intertwined with Marty's time travelling

Your first questions regarding why Doc faded and Marty and the time machine didn't have been discussed a lot on these forums. There's a detailed discussion about it in this thread.

In response to your second questions, you are right that the Doc at the end of the season is not the same Doc our Marty has traveled with. We don't know anything about whether he went to 1931 and got arrested or not, only that this Doc went to 1931 to research Marty's family. Although, my theory is that Doc travels to points in time (like getting the new timeline 1985 Marty to go to 2015) to put events in motion that are requirements for Marty and Doc's changes in order to keep the timeline circular and prevent paradoxes (which is my theory for why the tombstone didn't disappear at the end of Back to the Future Part III and why Doc built the time train after he seemed so against time travel in Part II), so under this theory, he'd have to go to 1931 and get arrested (if he hadn't already, then after he learned why Marty went there in the first place).

Telltale left it purposely ambiguous about what this Doc has been through at the end of the season, and I really hope they explore it if and when they make a season two of Back to the Future.

There's a lot of things that we don't know. The Doc we saw in episode 1 was close to 100 years old, but it's possible this Doc isn't that old (since we don't know how old Jules and Verne are in this timeline. If the writers were trying to tie the game into the animated TV show, then it's possible that Jules and Verne are just kids when their dad lives part time in 1980's-1990's Hill Valley). We also don't know if the previous Marty of this timeline traveled with Doc between 1985 and 1986, since this Doc has been living in Hill Valley part time since the events of Back to the Future Part III.

Your first questions regarding why Doc faded and Marty and the time machine didn't have been discussed a lot on these forums. There's a detailed discussion about it in this thread.

In response to your second questions, you are right that the Doc at the end of the season is not the same Doc our Marty has traveled with. We don't know anything about whether he went to 1931 and got arrested or not, only that this Doc went to 1931 to research Marty's family. Although, my theory is that Doc travels to points in time (like getting the new timeline 1985 Marty to go to 2015) to put events in motion that are requirements for Marty and Doc's changes in order to keep the timeline circular and prevent paradoxes (which is my theory for why the tombstone didn't disappear at the end of Back to the Future Part III and why Doc built the time train after he seemed so against time travel in Part II), so under this theory, he'd have to go to 1931 and get arrested (if he hadn't already, then after he learned why Marty went there in the first place).

Telltale left it purposely ambiguous about what this Doc has been through at the end of the season, and I really hope they explore it if and when they make a season two of Back to the Future.

There's a lot of things that we don't know. The Doc we saw in episode 1 was close to 100 years old, but it's possible this Doc isn't that old (since we don't know how old Jules and Verne are in this timeline. If the writers were trying to tie the game into the animated TV show, then it's possible that Jules and Verne are just kids when their dad lives part time in 1980's-1990's Hill Valley). We also don't know if the previous Marty of this timeline traveled with Doc between 1985 and 1986, since this Doc has been living in Hill Valley part time since the events of Back to the Future Part III.

It seems at though 'old' doc was always the one who got arrested for the speak easy in all the game versions of the timeline with the exception of the burnt hill valley one; in episode 3 we see Old Doc in FCB's picture, and in episodes 4 and 5, everyone remembers 'Carl Sagan' in 1931 even with FCB being present there. Here's how each of the docs timelines should go linearly;

OLD DOC
Goes through the time travels in the trilogy, eventually settles with Clara in a time zone other than the 1980's, goes back to 1931, gets arrested, goes back to 1986 briefly, and back to 1931 before being erased due to the FCB timeline

FCB
lives naturally, with his only time travels being back from 1986 to 1931 and several in 1931 before being erased

NEW DOC
seems to have been through all the time travels in the trilogy as he has the hoverboard and has been with Clara but the main difference from old doc is he has lived the past 7 months in the 1980's between the trilogy and game. He does seem to remember his original visit to 1931 including his motive.

It seems at though 'old' doc was always the one who got arrested for the speak easy in all the game versions of the timeline with the exception of the burnt hill valley one; in episode 3 we see Old Doc in FCB's picture, and in episodes 4 and 5, everyone remembers 'Carl Sagan' in 1931 even with FCB being present there. Here's how each of the docs timelines should go linearly;

OLD DOC
Goes through the time travels in the trilogy, eventually settles with Clara in a time zone other than the 1980's, goes back to 1931, gets arrested, goes back to 1986 briefly, and back to 1931 before being erased due to the FCB timeline

FCB
lives naturally, with his only time travels being back from 1986 to 1931 and several in 1931 before being erased

NEW DOC
seems to have been through all the time travels in the trilogy as he has the hoverboard and has been with Clara but the main difference from old doc is he has lived the past 7 months in the 1980's between the trilogy and game. He does seem to remember his original visit to 1931 including his motive.

I think you guys overcomplicate this a bit. The "new" Doc is basically the same as before, the only difference is that thanks to Marty he's able to come to terms with his father. Because of this he becomes more attached to his father's legacy and Hill Valley so he doesn't leave his home at the end of the third film. Apart from this his timeline stays the same as before because there's no interference to it since 1931. He goes to 1931 for the same reasons as the Doc in the beginning of the game and everything happens to him the same way because there is nothing that would change that.

Except that in the new timeline, everyone know who is the arsonist, so New Doc doesn't need to go back to that day to see who did it, and then isn't arrested.

That poses an interesting question. Does OUTATIME Doc remember going to 1931 to investigate the arson?

Officer Parker found out about Edna before the OUTATIME Doc arrived in 1931. But, we know that timelines take a while to change after affected by time travelers (2015 Hill Valley didn't change at all when Biff changed the past: it wasn't until they got to 1985 that they saw the difference, and also 1931 Hill Valley didn't change right away after Edna altered 1876). It's possible the timeline didn't catch up to OUTATIME Doc before he arrived in 1931, making his memories those of a Hill Valley that still considered the identity of the speakeasy arsonist to be an unsolved mystery.

That poses an interesting question. Does OUTATIME Doc remember going to 1931 to investigate the arson?

Officer Parker found out about Edna before the OUTATIME Doc arrived in 1931. But, we know that timelines take a while to change after affected by time travelers (2015 Hill Valley didn't change at all when Biff changed the past: it wasn't until they got to 1985 that they saw the difference, and also 1931 Hill Valley didn't change right away after Edna altered 1876). It's possible the timeline didn't catch up to OUTATIME Doc before he arrived in 1931, making his memories those of a Hill Valley that still considered the identity of the speakeasy arsonist to be an unsolved mystery.

It's likely this is the case, also didn't Doc return shortly before Edna left? Either way it's very obvious this doc did not come from a timeline in which hill valley was burned down.

Seems the primary reason Doc went back to 1931 was to find marty's grandmother, finding the arsonist was only a secondary reason. He also remarks that Marty saved him from making the biggest mistake of his life so it seems he's retained some new memories old doc didnt have

As for New Doc comming to 1931 even if Edna changed the past, I think a timeline is never realy erased. I even think that different timelines share the same past in some points in time.
Here are some exemples. Before the ripple effect, the timeline still lead to an unchanged future, which mean that any future time traveler can still come in the past to a point prior to the ripple effect. If Doc came after the ripple effect, I think he would still arrive in an intact Hill Valley, but Marty would not be here anymore.
I think ripple effect can have different effects depending if you're a time traveler or not.
For a time traveler, the timeline changes around him.
For a non-time traveler, the time traveler disappears from the timeline, but is not erased from their memories.
Now if the time traveler itself is erased, he does not disappear from past people memories either.
That's why everyone in 1931 still remembers Old Doc and First Citizen Brown at the end of the game, and also why Old Doc is still on the photograph of FCB.

Now for timelines sharing same past, it's very simple. By logic it's obvious that the 1955 in BTTF1 before Marty's arrival is the past of both Twin Pines and Lone Pine timeline, an this apply to every time travel. And that explain why three different future Martys arrive at the same point: their three timelines share the same past, which means that the events that will create the timelines will occur in the future, since there is no ripple effect in 1986.